Theory:

Every one of us would have seen our image in a mirror. The image formed in the mirror will be the same as we do in front of it. But, if you have noticed closely, there is a difference in the image left unnoticed.
 
Now, when we lift our left hand, it is seen that the right hand is raised on the mirror. Likewise, when we touch the right ear using the left hand, it appears as the right hand is touching the left ear.
 
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It is noted that the 'left side' appears as 'right side' and 'right side' appears as 'left side'. When we take a closer look, the image of our head will be at the top as it is. Here, the image does not appear upside down, but only the sides are interchanged.
 
Similarly, the image of a letter written on a piece of paper will be different in the plane mirror by interchanging the sides. This type of reversal where the right appears left, and vice-versa is known as lateral inversion.
 
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The word 'AMBULANCE' is written backwards in an ambulance van due to lateral inversion.
 
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This is because the drivers of other vehicles moving ahead of the ambulance can see the word 'AMBULANCE' in the right way around in their rear-view mirror and allow the vehicle to pass without blocking its path.
 
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Whenever we look at a plane mirror, we see the image by the phenomenon of lateral inversion.
 
Image properties of a plane mirror
  1. The image is always virtual and erect.
  2. The image is laterally inverted.
  3. The image size on the mirror will be the same as the object size.
  4. The object's distance from the mirror is equal to the image's distance from the mirror.